POLYURETHANE FOAMS FOR COMFORT APPLICATIONS

Abstract

Polyurethane foams that are hydrophilic but nonetheless have low compression sets are made from a combination of MDI and TDI prepolymers, water, and a polymer polyol. The foams optionally are made incorporating a phase change material in the foam formulation. The phase change material does not require encapsulation.

Claims

1. A flexible polyurethane foam comprising a reaction product of a reaction mixture that comprises a) an isocyanate mixture comprising a-1) a first isocyanate-functional prepolymer, which first isocyanate-functional prepolymer is a reaction product of at least one hydroxyl-terminated polymer of ethylene oxide and optionally a hydroxyl-functional branching agent and/or hydroxyl-functional chain extender with an excess of diphenylmethane diisocyanate of which diphenylmethane diisocyanate at least 50 weight-% is 4,4′-diphenylmethane diisocyanate, a-2) optionally diphenylmethane diisocyanate, wherein components a-1) and a-2) together have an isocyanate content of 5 to 15% by weight and contain 30 to 75 weight percent of oxyethylene units, based on the combined weight of components a-1) and a-2), and components a-1) and a-2) together constitute 40 to 60% of the total weight of the isocyanate mixture, a-3) a second isocyanate-functional prepolymer, which second isocyanate-functional prepolymer is a reaction product of at least one hydroxyl-terminated polymer of ethylene oxide and a hydroxyl-functional branching agent having at least three hydroxyl groups per molecule and a hydroxyl equivalent weight of up to 250 g/equivalent with an excess of toluene diisocyanate, and a-4) optionally toluene diisocyanate, wherein a-3) and a-4) together have an isocyanate content of 5 to 15% by weight and contain 30 to 75 weight percent of oxyethylene units, based on the combined weight of components a-3) and a-4) and 2 to 5% by weight of residues from the hydroxyl-functional branching agent, based on the combined weight of components a-3) and a-4); components a-3) and a-4) together constitute 40 to 60% of the total weight of the isocyanate mixture; and components a-1), a-2), a-3) and a-4) together constitute the entire weight of the isocyanate mixture; b) water; c) at least one polymer polyol comprising polymer particles dispersed in at least one base polyol, the base polyol being a polyether having at least 50% by weight oxypropylene units and a hydroxyl equivalent weight of 500 to 3000 g/equivalent; d) optionally a poly(ethylene oxide), the poly(ethylene oxide) being a homopolymer of ethylene oxide homopolymer or a random and/or block copolymer of at least 80% by weight ethylene oxide and up to 20% by weight of another alkylene oxide, the poly(ethylene oxide) having a number average molecular weight of 400 to 1200 g/mol; at least one of e) and f), wherein e) is at least one silicone surfactant; and f) is at least one ethylene oxide/higher alkylene oxide block copolymer, the block copolymer containing 40 to 90% by weight oxyethylene units and having a number average molecular weight of 1500 to 12,000 g/mol; and optionally g) at least one phase change material that has a melting or glass transition temperature of 25 to 37° C. and which does not contain isocyanate groups or isocyanate-reactive groups; wherein i) the isocyanate mixture constitutes 40 to 65% of the combined weights of components a-g; ii) water constitutes 15 to 41% of the combined weights of components a-g; iii) the at least one polymer polyol constitutes 8 to 20% of the combined weights of components a-g and the polymer particles constitute 0.5 to 10% of the combined weights of components a-g; iv) the poly(ethylene oxide) when present constitutes up to 5% of the combined weights of components a-g; v) the at least one silicone surfactant constitutes 0 to 3% of the combined weights of components a-g; vi) the at least one ethylene oxide/higher alkylene oxide block copolymer constitutes 0 to 3% of the combined weights of components a-g; vii) the at least one phase change material constitutes up to 15% of the combined weights of components a-g and viii) components a-g constitute at least 95% of the weight of the reaction mixture.

2. The flexible polyurethane foam of claim 1 wherein the phase change material comprises any one or more of a natural or synthetic wax such as a polyethylene wax, bees wax, lanolin, carnauba wax, candelilla wax, ouricury wax, sugarcane wax, jojoba wax, epicuticular wax, coconut wax, petroleum wax or paraffin wax.

3. The flexible polyurethane foam of claim 2 wherein the phase change material constitutes 2.5 to 10 percent of the total weight of components a-g.

4. The flexible polyurethane foam of claim 2 wherein components a-1) and a-2) together constitute 45 to 55% of the weight of the isocyanate mixture and components a-3) and a-4) together correspondingly constitute 55 to 45% of the weight of the isocyanate mixture.

5. The flexible polyurethane foam of claim 2 wherein the silicone surfactant and the ethylene oxide/higher alkylene oxide block copolymer each constitute 0.5 to 3% of the combined weights of components a-g.

6. The flexible polyurethane foam of claim 2 wherein the silicone surfactant contains 25 to 70% by weight polysiloxane, 10 to 75% by weight polymerized ethylene oxide and 0 to 10% by weight polymerized propylene oxide, based on the weight of the silicone surfactant.

7. The flexible polyurethane foam of claim 2 wherein the ethylene oxide/higher alkylene oxide block copolymer contains 40 to 90% oxyethylene units and has a number average molecular weight of 1,500 to 12,000.

8. The flexible polyurethane foam of claim 2 wherein the poly(ethylene oxide) constitutes 0.5 to 5% of the combined weights of components a-g.

9. A method of making a flexible polyurethane foam, comprising A. forming a reaction mixture by mixing: a) an isocyanate mixture comprising a-1) a first isocyanate-functional prepolymer, which first isocyanate-functional prepolymer is a reaction product of at least one hydroxyl-terminated polymer of ethylene oxide and optionally a hydroxyl-functional branching agent and/or a hydroxyl-functional chain extender with an excess of diphenylmethane diisocyanate of which diphenylmethane diisocyanate at least 50 weight-% is 4,4′-diphenylmethane diisocyanate, a-2) optionally diphenylmethane diisocyanate, wherein components a-1) and a-2) together have an isocyanate content of 5 to 15% by weight and contain 30 to 75 weight percent of oxyethylene units, based on the combined weight of components a-1) and a-2), and components a-1) and a-2) together constitute 40 to 60% of the total weight of the isocyanate mixture, a-3) a second isocyanate-functional prepolymer, which second isocyanate-functional prepolymer is a reaction product of at least one hydroxyl-terminated polymer of ethylene oxide and a hydroxyl-functional branching agent having at least three hydroxyl groups per molecule and a hydroxyl equivalent weight of up to 250 g/equivalent with an excess of toluene diisocyanate, and a-4) optionally toluene diisocyanate, wherein a-3) and a-4) together have an isocyanate content of 5 to 15% by weight and contain 30 to 75 weight percent of oxyethylene units, based on the combined weight of components a-3) and a-4) and 2 to 5% by weight of residues from the hydroxyl-functional branching agent, based on the combined weight of components a-3) and a-4); components a-3) and a-4) together constitute 40 to 60% of the total weight of the isocyanate mixture; and components a-1), a-2), a-3) and a-4) together constitute the entire weight of the isocyanate mixture; b) water; c) at least one polymer polyol comprising polymer particles dispersed in at least one base polyol, the base polyol being a polyether having at least 50% by weight oxypropylene units and a hydroxyl equivalent weight of 500 to 3000 g/equivalent; d) optionally a poly(ethylene oxide), the poly(ethylene oxide) being a homopolymer of ethylene oxide homopolymer or a random and/or block copolymer of at least 80% by weight ethylene oxide and up to 20% by weight of another alkylene oxide, the poly(ethylene oxide) having a number average molecular weight of 400 to 1200 g/mol; at least one of e) and f), wherein e) is at least one silicone surfactant; and f) is at least one ethylene oxide/higher alkylene oxide block copolymer, the block copolymer containing 40 to 90% by weight oxyethylene units and having a number average molecular weight of 1500 to 12,000 g/mol; and optionally g) at least one phase change material that has a melting or glass transition temperature of 25 to 37° C. and which does not contain isocyanate groups or isocyanate-reactive groups; wherein i) the isocyanate mixture constitutes 40 to 65% of the combined weights of components a-g; ii) water constitutes 15 to 41% of the combined weights of components a-g; iii) the at least one polymer polyol constitutes 8 to 20% of the combined weights of components a-g and the polymer particles constitute 0.5 to 10% of the combined weights of components a-g; iv) the poly(ethylene oxide) when present constitutes up to 5% of the combined weights of components a-g; v) the at least one silicone surfactant constitutes 0 to 3% of the combined weights of components a-g; vi) the at least one ethylene oxide/higher alkylene oxide block copolymer constitutes 0 to 3% of the combined weights of components a-g; vii) the at least one phase change material constitutes up to 15% of the combined weights of components a-g and viii) components a-g constitute at least 95% of the weight of the reaction mixture and B. reacting the reaction mixture to produce the foam.

10. The method of claim 9 wherein the phase change material constitutes 2.5 to 10 percent of the total weight of components a-g and the phase change material comprises any one or more of a natural or synthetic wax such as a polyethylene wax, bees wax, lanolin, carnauba wax, candelilla wax, ouricury wax, sugarcane wax, jojoba wax, epicuticular wax, coconut wax, petroleum wax or paraffin wax.

11. The method of claim 10 wherein the silicone surfactant and the ethylene oxide/higher alkylene oxide block copolymer each constitute 0.5 to 3% of the combined weights of components a-g, the silicone surfactant contains 25 to 70% by weight polysiloxane, 10 to 75% by weight polymerized ethylene oxide and 0 to 10% by weight polymerized propylene oxide, based on the weight of the silicone surfactant and the ethylene oxide/higher alkylene oxide block copolymer contains 40 to 90% oxyethylene units and has a number average molecular weight of 1,500 to 12,000.

12. A cushion comprising a flexible polyurethane foam of claim 1.

13. The cushion of claim 12, which is a pillow, mattress topper, mattress, comforter, furniture seat or back, automotive seat or back; quilt or article of insulated clothing, or a pad for a prosthetic limb.

14. The cushion of claim 12, wherein the flexible polyurethane foam, when dried to a constant weight, has a density of 48 to 80 kg/m.sup.3 and a compression set of 10% or less.

15. The cushion of claim 12 wherein the flexible polyurethane foam, when dried to a constant weight, exhibits a latent heat of at least 2.5 J/g at 27° K and a moisture wicking time of 5 seconds or less.

Description

EXAMPLES 1-3

[0135] Comparative Samples 1-3 are made from recipes as set forth in Table 2. Results of the foam testing of these samples are as indicated in Table 2.

TABLE-US-00002 TABLE 2 Parts by Weight Ingredient Ex. 1 Ex. 2 Ex. 3 Water 29.5 31.25 31.25 Surfactant A 1.75 0 1.75 Surfactant B 1.75 1.75 0 CPP 17 17 17 PCM 0 0 0 Poly(EO) 0 0 0 Polyisocyanate 1 25 25 25 Polyisocyanate 2 25 25 25 Results Moisture Wicking, s 4 4 4 Density, lb/ft.sup.3 (kg/m.sup.3) 4.61 (73.8) 4.58 (73.3) 4.78 (76.5) Airflow, scfm (L/s) 3.04 (1.43)  0.3 (0.14) 1.09 (0.51) 90% Compression Set, % 9.7 9.2 7.2 Latent Heat at 27° C. (J/g) 0 0 0 k-factor 0.3 0.3 0.3

[0136] These results demonstrate the effect of using a 50/50 mixture of Polyisocyanates 1 and 2, together with three different surfactant packages. Ex. 1 is a direct comparison with Comp. Sample C (Table 1), the difference being a higher level of branching in the TDI prepolymer of Example 1 (Prepolymer 1, 3.8 weight-% branching agent) compared to the TDI prepolymer of Comparative Sample C (Prepolymer 3, 1.1 weight-% branching agent). The more highly branched Prepolymer 1 leads to a dramatic reduction in compression set (9.7% vs. 84.6% for Comp. Sample C).

[0137] Example 1 in comparison with Comp. Sample B demonstrates the effect of the ratio of components a-1) plus a-2) to components a-3) plus a-4). Too much of components a-3) plus a-4) leads to a large increase in compression set (31.2 for Comp. Sample B vs. only 9.7% for Example 1.

[0138] Examples 2 and 3 show the effect of using only one of Surfactants A and B. Very low compression sets are obtained in all of Examples 1-3, but airflows are much lower when only one of the surfactants is present, as in Examples 2 and 3. Latent heats at 27° C. are zero due to the lack of a phase change material.

Comparative Samples F and G

[0139] Comparative Samples F and G are made from recipes as set forth in Table 3. Results of the foam testing of these samples are as indicated in Table 3.

TABLE-US-00003 TABLE 3 Parts by Weight Ingredient Comp. F* Comp. G* Water 29.5 29.5 Surfactant A 1.75 1.75 Surfactant B 1.75 1.75 CPP 25 5 PCM 0 0 Poly(EO) 0 0 Polyisocyanate 1 25 25 Polyisocyanate 2 25 25 Results Moisture Wicking, s 4 4 Density, lb/ft.sup.3 (kg/m.sup.3) 4.77 (76.3) 4.95 (79.2) Airflow, scfm (L/s) 3.94 (1.85)  8.4 (3.95) 90% Compression Set, % 14.7 84.6 Latent Heat at 27° C. (J/g) 0 0 k-factor 0.3 0.3 *Not an example of the invention.

[0140] Comp. Examples F and G illustrate the effect of increasing (Comp. F) or decreasing (Comp. G) the amount of polymer polyol in conjunction with the 50/50 blend of Polyisocyanates 1 and 2, in comparison to Ex. 1 (Table 2). Compression set increases somewhat for Comp. Sample F. Even at this moderately increased level the compression set is higher than is wanted for bedding applications. Compression set becomes extremely high in Comp. Sample G. Again, the latent heat is zero in all cases due to the lack of phase change material.

EXAMPLES 4-8

[0141] Examples 4-8 are made from recipes as set forth in Table 4. Results of the foam testing of these samples are as indicated in Table 4.

TABLE-US-00004 TABLE 4 Parts by Weight Ingredient Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Water 24.5 29.5 27.0 22.5 24.5 Surfactant A 1.75 1.75 1.75 1.75 1.75 Surfactant B 1.75 1.75 1.75 1.75 1.75 CPP 17 17 15 13 15 PCM 5 0 2.5 10 5 Poly(EO) 0 5 2 2 2 Polyisocyanate 1 25 25 25 25 25 Polyisocyanate 2 25 25 25 25 25 Results Moisture Wicking, s 4 4 4 4 4 Density, lb/ft.sup.3 (kg/m.sup.3) 4.14 (66.2) 4.07 (65.1) 4.27 (68.3) 4.52 (72.3) 4.93 (78.9) Airflow, scfm (L/s) 1.55 (0.73)  5.3 (2.49) 4.28 (2.01) 1.84 (0.86) 3.05 (1.43) 90% Compression Set, % 2.7 3.8 2.8 2.9 4.2 Latent Heat at 27° C. (J/g) 14.9 0 4.7 20.1 14.1 k-factor 0.3 0.3 0.3 0.3 0.3 *Not an example of the invention.

[0142] All of Examples 4-8 exhibit very low compression sets.

[0143] The presence of the phase change material in Example 4 has three effects, as shown in comparison to Example 1. Compression set becomes even lower than Example 1, and a positive latent heat is seen at 27° C. Some loss of airflow is seen.

[0144] Example 5 shows the effect of including component f) in the reaction mixture, in the absence of a phase change material. When compared with Example 1, compression set is significantly lower and a higher airflow is obtained. The latent heat at 27° C. is zero due to the lack of a phase change material.

[0145] Examples 6-8 show the effect of including both component f) and the phase change material. Compression sets are extremely low and airflows are improved relative to Example 4, which has the phase change material but no component f). This is seen even at a very high level of phase change material (Ex. 7). Airflows for Examples 6 and 8 are comparable or higher than those of Example 1, despite the presence of the phase change material.